The present invention relates to a process for producing substituted thiocarbamates in a continuous cycle.
It is known from the literature that it is possible to synthesize thiocarbamates by reacting a secondary amine with carbon monoxide and sulphur in a suitable solvent and thereafter subjecting the product obtained to alkylation.
The reactions are as follows: ##STR1## wherein: R.sub.1, R.sub.2 may be the same or different, consisting of alkyl, cycloaklyl or aralkyl radicals, or may form together a bivalent polymethylene radical.
R.sub.3 =an alkyl, cycloalkyl or aralkyl radical. PA1 X=a substituted group consisting of halide, sulphate or sulphonate.
In essence, it happens that in reaction (1) the secondary amine reacts with the carbon monoxide and sulphur to give rise to a substituted ammonium salt of thiocarbamic acid, after which in reaction (2) this salt reacts with an alkylating agent, forming the substituted thiocarbamate.
Deep study of the mechanism by which the aforesaid known reactions occur and a long series of experiments have now enabled the Applicants to develop an improved process and apparatus for producing substituted thiocarbamates.
In effect, heretofore the first of the above-mentioned reactions has always been conducted in the presence of an excess of sulphur by mixing equal molar amounts of secondary amine and sulphur in the presence of carbon monoxide.
Moreover, the two reactions have always been carried out separately and each in a discountinuous manner.